Biologia da reprodução de cinco especies de melastomataceae da restinga de Marica-RJ

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

The phenology, floral biology and reproduction of Tibouchina reichardtiana Cogn., T. trichopoda (OC.) Baill. var. trichopoda, T.trichopoda (OC.) Baill. var. tibouchinoides (OC.) Cogn., Marcetia taxifoLia (St.Hil.) DC., Rhynchanthera dichotoma (Desr. ) DC. And Pterolepis glomerata (Rottb.) Miq. (Melastomataceae) were studied in the restinga of Marica, Rio de Janeiro, from 1990 to 1993. Four floral phonological patterns were detected: seasonal, long, episodic and continuous. Each pattern was characterised by the amount of syncronous blooming, the duration of each blooming, and floral density. The majority of species studied had its blooming peak within the rainy season. These Melastomataceae release their pollen through terminal pores, and their androecium seems to be very actractive to bees. Their stigma is small, hard, with an external portion (for the adherence of pollen) and an internal, papillate part (directly related to the germination and development OI pollen tube). Flowers were visited by 18 species of predominantly polyletic bees. Pollen liberation occurs by bee vibration, which is also necessary for its adherence to the stigma. Bee visitation rate increased in gradient III during the rainy season. Xylocopa ordinaria seems to be the principal pollinator for the majority of plants studied. Pollen availability for visitors represents a continuous source of food for bee s communities in the restinga. All species studied are self-compatible with considerable pollination efficiency, and high reproductive success; they use mixed reproduction systems, predominantly self-fertilization. The rate between self-fertilization and cross-fertilization of each species is determined by pollinator feeding behavior, and by flower daily production. During "mass" blooming periods, when intraplant visits are longer, the frequency of geytonogamy increases. In lower flower production periods, pollinators visit a higher number of plants in a given collecting round, raising the frequency of zenogamy. Sympatric species of Tibouchina show similar floral morphology, and share the same pollinators, which gather pollen in correlated body regions. F1 Seedlings originated by interspecific crossbreeding prove the absence of pre-zygotic barriers within Tibouchina species. Floral constancy and pollinator s feeding strategy warrant the intraspecific pollen flow.

ASSUNTO(S)

plantas - fertilização polinização abelha - polen fenologia melastomataceae

ACESSO AO ARTIGO

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